FR2841341A1 - Method for determining the output current and load torque of a vehicle generator, comprises measurement of speed and excitation current and processing them using stored tables and curves - Google Patents

Abstract

The output current and/or load torque of a vehicle generator (9) are determined by measuring the generator speed and excitation current. The generator speed is measured by a dedicated equipment (8) and the generator excitation current by a module (6) within the generator regulator (7). The data obtained is supplied to a processor (10) which produces the output current using stored test tables with compensation for air gap width : An independent claim is also included for equipment to measure generator speed and excitation current.

Description

1 a16.

  Field of the invention The present invention relates to a method for determining the output current of a vehicle generator, the output voltage of which

  is regulated by a generator regulator.

  s The invention also relates to a device for setting

in this process.

  STATE OF THE ART The load torque and the output current of a vehicle generator have important parameters or characteristic quantities for carrying out an energy balance in an on-board electrical network.

  or for effective management of the engine of a motor vehicle.

  The generator output current is usually calculated from the generator rotation speed n, the excitation current I err and the air gap d between the rotor and the stator using a characteristic field defined for each generator. The excitation current Ierr of the generator is calculated from the working ratio (T conduction / T conduction blocking) of a switching transistor switching on the excitation field, the temperature of the excitation field T as determined by example indirectly from the temperature of the engine enclosure, the resistance R of the excitation field as well as the parasitic loss resistors in the excitation path Rpar, values that are evaluated. To determine the current of the generator Igen, we apply the formula: Igen = f (n, T, R. Rpar, Ubat, d) s The speed of rotation n of the generator and the output voltage Ubat of the generator can be measured. On the contrary, the temperature of the excitation field T. the resistance of the excitation field R and their dependence on temperature as well as the parasitic loss resistances R by wind of the quantities difficult to determine but these quantities influence the result so strongly. The deviations for the effective temperature T of the excitation field, those in the determination of the resistance R of the excitation field and those of the voltage actually applied to the excitation field are directly reflected in the calculation of the current of

Igen output from the generator.

  ss To calculate the load torque Mgen of the generator, we apply the following relation: Mgen = f (Igen, Ubat, n) As it appears, the result is an output current of

  relatively imprecise Igen generator.

  The accuracy of calculating the output current of the generator Igen or the load torque of the generator Mgen for calculating the load balance or for managing the engine in particular the operation of the engine at idle is falble. This is why the determination of

  these quantities require relatively a lot of calculation.

  Aim of the invention The aim of the present invention is to develop the precision o of the calculation of the generator output current or of the load torque and of

  at the same time reduce the importance of the calculations.

  Disclosure of the invention To this end the invention relates to a method of the type defined above, characterized in that - the speed of rotation of the generator is measured, - the excitation current is measured, - the values are supplied measured at a treatment installation, and - the generator output current is determined from the measured values. o The invention also relates to a device for solving this problem, this device is characterized by an installation for measuring the rotational speed of the generator, an installation for measuring the excitation current, the measured values being transmitted to an installation of processing which determines the generator output current at

from the measured values.

  The essential characteristics of the invention are preferably to directly measure the excitation current in the generator regulator and to supply the value measured by means of an interface suitable for a control device ( processing unit) to calculate from the generator output current or the load torque. Direct measurement of the excitation current makes it possible to avoid the above-mentioned inaccuracies in the evaluation of the excitation current and to considerably improve the calculation of the generator output current.

and the load torque.

  ss Thus, the calculation of the output current of the generator Igen and the load torque Mgen in the control device is linked by the following relations: Igen = f (n, Ierr, d) Mgen = f (Igen, Ubat, n) The generator output current and / or the wind load torque preferably determined from the characteristic curves

  or tables saved for example in the control unit.

  s The system contains in memory for example a field of characteristic curves of the generator current / rotational speed or in core load torque / rotational speed so that the generator output current or the generator load torque can be supplied directly taking into account the other quantities (n, Ubat, d). A choice

  o you can also calculate the output current or the load torque.

  By direct measurement of the excitation current (using an appropriate current measurement device), we will have quantities which are determined in a relatively precise way to obtain the output current of the generator and the load torque. . The only large, unknown quantity is the air gap d of the generator. For the air gap, an average value supplied by the manufacturer is usually used. he

  can come from a relatively imprecise working air gap.

  To further improve the precision in the generator control (control state measurement) one can adjust a generator output current actually measured, and that one obtains for the predetermined excitation current and a rotation speed given, to compensate for the characteristic curves recorded in the system and to adapt them to the effective air gap of the generator. For example, a correction coefficient can be determined with which the output current of the generator or the load torque, recorded in the system, is corrected to eliminate the influence of the air gap. Optionally from the measurement made on a test tank, we can also calculate inversely the effective air gap d which can then be used to determine the generator output current

or the load torque.

  Drawings The present invention will be described below in more detail with the aid of an exemplary embodiment represented in the annexed drawings in which: - Figure l shows an example of a field of characteristics neck 3s speed / speed of rotation of a generator, - Figure 2 shows a flowchart presenting the process for determining the current of the generator, - Figure 3 is a schematic view of a device for determining the

  output current of a motor vehicle generator.

  Description of an embodiment

  Figure l shows a field of current generator characteristics / rotational speed recorded in a system. This field represents the influence of the excitation current I err and the air gap d on the output current Igen supplied by the generator. As it appears, the output current Igen of the generator increases with the current

excitation Ierr (Ierrl> Ierr3).

  The lower current characteristic curve (Ierr3) further shows the influence of the air gap d; it appears that the generator output current Igen decreases slightly with the increase in the air gap. To eliminate the imprecision linked to different air gap values d in the calculation of the generator output current and the generator load torque, when measuring on the test tank, the actual output current is used generator measure. From the measurement of the test strip, a generator current is obtained under the defined conditions (excitation current I err and speed of rotation n).

  where the characteristics can be corrected correspondingly.

  Beside the characteristic current curves, the characteristic torque curves have also been recorded in the system (these curves are not shown); from these curves we can

  fire the instantaneous or current load torque.

  s Figure 2 shows a flowchart showing the method for easily determining the output current Igen of the generator. In the method for determining the output current Igen, in a first step 1, the rotation speed n of the generator is used first and in a second step 2, the excitation current I err is measured. In a third step, the current Igen of the generator is determined from the measured values. This is done using characteristic curves or tables recorded in an installation

  processing (control unit).

  In the exploitation of the characteristic curves one takes into account the effective value of the air gap d of the generator; this greatness

  is that obtained previously in the measurements on the test tank.

  By direct measurement of the excitation current Ierr we can

  very precisely define the output current Igen of the generator.

  FIG. 3 shows a device for determining the output current Igen of a vehicle generator 9, the output voltage of which is regulated by a generator regulator 7. The device further comprises an installation 8 for measuring the speed of rotation n of the generator and an installation 6 to measure the excitation current I err. The measured values are applied to a processing installation 10 which detects the generator output current Igen from the measured values. We can directly extract the output current from the generator Igen for example by using tables or characteristic curves in

registered in the system.

NOMENCLATURE

  1-3 Previous step 6 Measuring installation s 7 Generator regulator 8 Speed measurement device 9 Generator to Igen processing unit Generator current lo Ierr Air excitation current n Rotation speed (speed)

Claims (5)

RESELL I CATI ONS   1) Method for determining the output current (Igen) of a vehicle generator whose output voltage is regulated by a generator regulator, characterized in that - the rotation speed (n) of the generator is measured, - the excitation current (Ierr) is measured, - the values measured are supplied to a treatment installation, and - the generator output current (Igen) is determined from the values 0 their measurements.   2) Method according to claim l, characterized in that   the excitation current (I err) is measured in the generator regulator.   3) Method according to any one of claims l or 2,   characterized in that the output current (Igen) and / or the load torque are determined from   characteristic curves or tables recorded in the system.   4) Method according to claim l, characterized in that by determining the output current of the generator (Igen) a compensation of the values is carried out with an output current actually measured   (Igen) of the generator to take account of the effective air gap (d).    ) Method according to claim 1, characterized in that the value of the effective air gap (d) is determined from the measurements made on the test tank and is taken into account to determine the current of   output (Igen) or the load torque.   6) Device for determining the output current (Igen) of a vehicle generator, the output voltage of which is regulated by a 3s generator generator regulator, characterized by - an installation for measuring the rotation speed of the generator (n), - an installation to measure the excitation current (Ierr), the measured values being transmitted to a processing installation   which determines the output current (Igen) of the generator from the values their measurements.   s 7) Device according to claim 6, characterized in that the installation for measuring the excitation current (I err) is part of the re generator regulator.